Allergy - disease of the modern age

For the first time that I came across with the allergy was when my sister had a cold that lasted too long so we finally realized that it has to be something else that just a simple cold. She was very young and ever since she's been fighting against this incurable disease. She was swollen and tired in spring and summer when everyone else enjoyed fresh air and spending time outside. At night she would inhale and during the day she would cough and choke.

The other day we spoke on the phone and when I asked how's she doing, she said - tired and swollen. So, nothing changed during all these years. There was no progress and that's what scares me.
It scares me because I have the same problem with my daughter today.
She woke up in the morning looking like this.

Her eyes are blurry and the eye bags are really concerning me.
The problem is that you don't have any smart solution, just to watch your kid suffering. I mean, we tried a lot of things... but I can't say that we had any success.
First, we tried to build the immune system, we mixed smoothies in the morning, bought a different supplement, tried natural pills...(It's really hard for me to accept that she will have to take a pill for the rest of her life).
A few months ago I bought a pillow filled with buckwheat flakes. It might have helped a little but not as much as we hoped it would.

Maybe the best advice that I got was the one from a grandfather of a friend of mine, a very respectable doctor. He said, 'try to get her used to it. If a person is, for example, allergic to strawberries you should give her every day just a small piece of it. The same is with all other allergies - fight, don't ever give up and don't close yourself in the house. And do whatever you can to build up the immune system.'
For now, we are trying to live by that exact rules. (If you have some more please share it with me).

Well, there is one more solution that I find the best one, but not everyone can afford that. It's the sea or any place that has a clean air. When school is over and we pack our bags and move to our beach house, we have no more problems (with allergies or with anything else:)) The problem is contradictory, you have an allergy to the things in nature but they are much more noticeable in the city than in the heart of the nature itself. I realized that pollution, this smog all around us, is also a cause of a problem.

My friend had kids that had really bad allergies and they were in the hospital on the daily basis. One day he decided to move to the countryside to finish the agony. The kids haven't visited the doctor ever since. If we couldn't have a chance to keep this under control, I'm seriously considering to do the same.